Until recently, medical literature has recognized four types of insomnia, including sleep onset insomnia (e.g., trouble falling asleep at bedtime), sleep maintenance insomnia (e.g., disturbed sleep during the night), early morning awakening, and transient insomnia (e.g., new environment, first night in hotel syndrome). However, according to the National Sleep Foundation's 2005 “Sleep in America” poll, about 20% of total respondents and about 50% of respondents reporting insomnia symptoms complained of waking up too early and having difficulty returning to sleep at least a few nights a week (results available, on the worldwide web at sleepfoundation.org). This type of insomnia includes “middle-of-the-night” insomnia, “late night” insomnia, “prolonged awakening after sleep onset” insomnia, “sleep maintenance” insomnia, and insomnia that follows after “middle-of-the-night” awakening, each of which has a component of interrupted sleep.
More particularly, patients with “middle-of-the-night” (MOTN) insomnia generally do not have problems initially falling asleep, but wake up prior to their intended wake time (during their normal sleep time), usually with about 3 to 4 hours of sleep time remaining. These patients require a treatment intervention that would reduce their wake time during their sleep time after awakening without leaving residual sedative effects in the morning. Unfortunately, currently available hypnotic medications are unsuitable for treating MOTN insomnia because they are slow to induce sleep (e.g., zaleplon) and/or require administration prior to about 7 to 9 hours in bed to avoid residual sleepiness in the morning (e.g., available dosage forms of zolpidem, eszopiclone, and zopiclone). Also, administration of most presently available hypnotics is prophylactic, resulting in unnecessary medication and overmedication of persons who require treatment for their MOTN insomnia a few nights a week.
Clearly, there remains a need for appropriate treatments for persons with MOTN insomnia. The present invention fulfills this and other needs.